I'm running a proprietary driver for my Radeon HD 7770. CPU is an AMD Phenom II X6. I have no problems running Xonotic and Nexuiz outside of Steam. Steam starts up just fine. When I try to start Team Fortress 2 inside of Steam, I see the Valve splash screen (dude with a valve in the back of his head), and that is followed by a ghostly white scene of what looks like a farm cooperative grain elevator or something similar. The moment that it appears that the game itself should start up, the whole scene dies, and I am left looking at the Steam UI. I am left with the impression that TF2 is crashing.

I am not very knowledgeable about system-level issues, there are errors thrown in the log output, but I don't know it they are all fatal or if only a subset is the problem, so I am hoping that someone here can tell me if they know what is wrong, and what I can do to fix it. I'm hoping for explicit instructions on what to do.